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Example
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HVAC Products
active. If that setpoint is set inactive (operating line 180 =
limitation of the return temperature during the time the legionella function is active.
When both the heating and the d.h.w. circuit call for heat and maximum limitation of the
return temperature acts on both circuits, the higher of the two limit values applies.
If, with plant type 1–3, maximum limitation of the return temperature is deactivated (en-
try ---), the d.h.w. temperature will be controlled according to the return temperature
acquired with sensor B71 because there is no sensor in the d.h.w. flow. The controlled
setpoint is the sum of the current d.h.w. setpoint plus the charging boost (operating
line 116).
The current d.h.w. setpoint is generated internally and can be visualized as follows:
Select operating line 26 and press
26.3
Maximum limitation of the secondary return
temperature
The secondary return temperature of both the heating and the d.h.w. circuit can be
limited at a maximum, depending on the type of plant. The limit value is to be entered
on operating line 177 as a reduction to the current limit value of the maximum limitation
of the primary return temperature.
This function can become active only when the respective maximum limitation of the
primary return temperature (heating circuits or d.h.w.) is switched on. Maximum limita-
tion of the primary return temperature can be deactivated on operating line 171 for the
heating circuit return (separately for each heating circuit), and on operating line 176 for
the d.h.w. return.
With plant type no. 2–2, the parameters are selected as follows:
Operating line 171 = 1
Operating line 172 = 70 °C
Operating line 173 = 7
Operating line 174 = 10 °C
Operating line 175 = 50 °C
Operating line 176 = 55 °C
Operating line 177 = 5 °C
When the outside temperature changes, the maximum limitations will change also:
Outside tem-
perature
Primary side
15 °C
50 °C (operating
line 175)
–5 °C*
60.5 °C**
–20 °C
70 °C (operating
line 172)
*
With shifting compensation
** Equation according to subsection 26.2.2 "Maximum limitation in heating mode
Basic documentation RVD240
26 Function block DRT and maximum limitation of the return temperature
.
Maximum limitation of return temperature heating circuit
2 ON
Upper constant value
Slope
Start of compensation at an outside temperature of
10 °C
Lower constant value
Maximum limitation of the return temperature in the
d.h.w. circuit
Reduction on the secondary side
Heating circuit 1
Secondary side
45 °C (operating
line 175...177)
55.5 °C
65 °C (operating
line 172...177)
), there will be no maximum
- - -
D.h.w. circuit
Primary side
Secondary side
55 °C (oper-
50 °C (operating
ating line
line 176...177)
176)
CE1P2384en
27.05.2004
93/126
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